Memory arrays and associated methods of manufacturing

ABSTRACT

Memory arrays and associated methods of manufacturing are disclosed herein. In one embodiment, a memory array includes an access line extending along a first direction and a first contact line and a second contact line extending along a second direction different from the first direction. The first and second contact lines are generally parallel to each other. The memory array also includes a memory node that includes a first memory cell electrically connected between the access line and the first contact line to form a first circuit, and a second memory cell electrically connected between the access line and the second contact line to form a second circuit different from the first circuit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 12/617,501 filed Nov. 12, 2009, now U.S. Pat. No. 8,619,456, which is incorporated herein by reference.

TECHNICAL FIELD

The present technology is directed generally to memory arrays and associated methods of manufacturing.

BACKGROUND

Memory cells (e.g., floating-gate transistors or PCRAM cells) are typically arranged in an array connected to a grid formed by a plurality of Word lines and Bit lines. The Word lines are generally parallel to one another and perpendicular to the Bit lines. Each of the memory cells forms a node of the array, and each node is connected to a particular pair of Word lines and Bit lines. In operation, each memory cell may be individually accessed by energizing a particular pair of Word lines and Bit lines while floating or oppositely biasing the rest of the Word lines and Bit lines.

The conventional arrangement of the memory array, however, cannot accommodate more than one memory cell per node. If the memory array includes two memory cells per node that are connected to a pair of Word lines and Bit lines, energizing the pair of Word lines and Bit lines would simultaneously energize the two parallel memory cells. Thus, the two memory cells may not be individually addressed or accessed. Accordingly, certain improvements to the memory arrays may be needed to accommodate more than one memory cell per node.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic circuit diagram of a non-orthogonal memory array in accordance with embodiments of the technology.

FIG. 1B is a schematic circuit diagram of a memory node in the non-orthogonal memory array of FIG. 1A.

FIG. 2 is a perspective view of one implementation of the non-orthogonal memory array in FIG. 1 in accordance with embodiments of the technology.

FIG. 3 is a top view of the non-orthogonal memory array in FIG. 2 in accordance with embodiments of the technology.

FIG. 4A is a perspective view of a two-cell memory sub-assembly useful for the non-orthogonal memory array in FIG. 2 in accordance with embodiments of the technology.

FIG. 4B is a cross-sectional view of another two-cell memory sub-assembly useful for the non-orthogonal memory array in FIG. 2 in accordance with embodiments of the technology.

FIGS. 5A-5K are top and cross-sectional views of a portion of a substrate material undergoing a process useful for forming several embodiments of the non-orthogonal memory array of FIG. 2 in accordance with embodiments of the technology.

FIG. 6 is a schematic circuit diagram of an orthogonal memory array configured to accommodate multiple memory cells per node in accordance with other embodiments of the technology.

FIG. 7 is a top view of one implementation of the orthogonal memory array in FIG. 6 in accordance with embodiments of the technology.

FIGS. 8A-8F are top and cross-sectional views of a portion of a semiconductor substrate undergoing a process useful for forming several embodiments of the orthogonal memory array of FIG. 7 in accordance with embodiments of the technology.

DETAILED DESCRIPTION

Several embodiments of the present technology are described below with reference to memory arrays and associated methods of manufacturing. Many details of certain embodiments are described below with reference to semiconductor substrates. The term “semiconductor substrate” is used throughout to include a variety of articles of manufacture, including, for example, individual integrated circuit dies, sensor dies, and/or dies having other semiconductor features. Several of the processes described below may be used to form memory arrays on a wafer or a portion of a wafer. The wafer or wafer portion (e.g., wafer form) can include an unsingulated wafer or wafer portion, or a repopulated carrier wafer. The repopulated carrier wafer can include singulated elements (e.g., dies) surrounded by an adhesive material (e.g., a flexible adhesive) and a generally rigid frame. Many specific details of certain embodiments are set forth in FIGS. 1-8F and in the following text to provide a thorough understanding of these embodiments. Several other embodiments can have configurations, components, and/or processes different than those described in this disclosure. A person skilled in the relevant art, therefore, will appreciate that additional embodiments may be practiced without several of the details of the embodiments shown in FIGS. 1-8F.

FIG. 1A is a schematic circuit diagram of a portion of a non-orthogonal memory array 100 in accordance with several embodiments of the technology, and FIG. 1B is a schematic circuit diagram of a memory node 106 in the non-orthogonal memory array of FIG. 1A. As used herein, the term “orthogonal” generally describes a positional relationship that is perpendicular. The term “non-orthogonal” generally describes a positional relationship that is oblique or canted. As shown in FIG. 1, the memory array 100 can include a grid 101 and a plurality of memory nodes 106 carried by the grid 101. Even though only certain components of the memory array 100 are shown in FIG. 1A, in certain embodiments the memory array 100 may also include peripheral circuits, registers, and/or other suitable components.

The grid 101 can include a plurality of contact lines 102 and a plurality of access lines 104. The contact lines 102 are generally parallel to one another, and the access lines 104 are generally parallel to one another. In the illustrated embodiment, the contact lines 102 include first to seventh contact lines 102 a-102 g, and the access lines 104 include first to fourth access lines 104 a-104 d. In other embodiments, the contact and access lines 102 and 104 may include a greater or smaller number of lines.

The contact and access lines 102 and 104 can be non-orthogonal relative to one another. In the illustrated embodiment, the individual contact and access lines 102 and 104 are at an angle α of about 63°. In other embodiments, the individual contact and access lines 102 and 104 can be at other suitable angles based on the dimensions and/or relative arrangements of the contact and access lines 102 and 104, as discussed in more detail below with reference to FIG. 3. In further embodiments, the contact and access lines 102 and 104 can also be generally orthogonal while configured to accommodate the memory nodes 106 with two memory cells, as discussed in more detail below with reference to FIGS. 6-8F.

The memory nodes 106 are individually connected to the contact and access lines 102 and 104. As shown in FIG. 1B, the individual memory nodes 106 can include a first rectifier 108 a, a first memory cell 110 a, a second memory cell 110 b, and a second rectifier 108 b connected to one another in series. The input terminals of the first and second rectifiers 108 a and 108 b form an input point 114 electrically coupled to a corresponding second access line 104. The output terminals of the first and second rectifiers 108 a and 108 b are electrically connected to the corresponding first and second memory cells 110 a and 110 b, respectively. In the illustrated embodiment, the first and second rectifiers 108 a and 108 b each include a diode. In other embodiments, the first and second rectifiers 108 a and 108 b can also include a bipolar transistor, a junction field effect transistor (“JFET”), a metal oxide field effect transistor (“MOSFET”), and/or other suitable types of rectifying device.

The first and second memory cells 110 a and 110 b (collectively referred to as “memory cells 110”) can include any suitable memory cell configurations. For example, in a particular embodiment, the memory cells 110 can include a phase change random access memory (“PCRAM”) component constructed from chalcogenide glass, as described in more detail below with reference to FIGS. 4A and 4B. In one embodiment, the PCRAM structure is switchable between two states. In other embodiments, the PCRAM structure may be switchable between four, eight, or another number of states. In further embodiments, the memory cells 110 can include a floating gate transistor and/or other suitable types of memory structures.

The memory nodes 106 can include a first output point 107 a and a second output point 107 b electrically connected to corresponding contact lines 102 (e.g., fourth and fifth contact lines 102 d and 102 e, respectively, as shown in FIG. 1B) via optional third rectifiers 112. In the illustrated embodiment, the third rectifier 112 includes a diode. In other embodiments, the third rectifier 112 can also include a bipolar transistor, a JFET, a MOSFET, and/or other suitable types of rectifying device. In further embodiments, the third rectifier 112 may be omitted, and a direct electrical link (e.g., a metal trace, a metal wire, and/or other conductive coupler) may directly connect the output points 107 a and 107 b to the corresponding contact lines.

One feature of several embodiments of the memory array 100 is that the memory cells 110 in the memory nodes 106 are individually connected to different pairs of the contact and access lines 102 and 104 to form different circuits. For example, as shown in FIG. 1B, the first memory cell 110 a is connected between fourth access line 104 d and the fifth contact line 102 e forming a first circuit. The second memory cell 110 b is connected to the fourth access line 104 d and the fourth contact line 102 d forming a second circuit. The first and second circuits are electrically isolated from each other.

The foregoing feature allows each of the memory cells 110 in the individual memory nodes 106 to be individually addressed or accessed. For example, the first and second memory cells 110 a and 110 b of the memory node 106 may be individually accessed by energizing (1) the fourth access line 104 d and the fourth contact line 102 d or (2) the fourth access line 104 d and the fifth contact line 102 e. As shown in FIG. 1B, to access the first memory cell 110 a, the fourth access line 104 d and the fifth contact line 102 e may be energized (e.g., by reversing the polarity relative to other access lines). As a result, electrical current may flow between the fourth access line 104 d and the fifth contact line 102 e via a path formed by the input point 114, the first rectifier 108 a, the first memory cell 110 a, the first output point 107 a, and the optional third rectifier 112. Thus, the state and/or other information stored in the first memory cell 110 a may be altered or accessed. While accessing the first memory cell 110 a, the second memory cell 110 b can retain its current state because the fourth contact line 102 d is reversely biased or kept floating. After the first memory cell 110 a is accessed, the second memory cell 110 b may be accessed by energizing the fourth access line 104 d and the fourth contact line 102 d while reversely biasing or floating the fifth contact line 102 e.

FIG. 2 is a perspective view of one implementation of the non-orthogonal memory array 100 in FIG. 1, and FIG. 3 is a top view of the non-orthogonal memory array 100 in FIG. 2 in accordance with embodiments of the technology. In FIGS. 2 and 3, inter-component insulation of the memory array 100 is removed for clarity.

Referring to both FIGS. 2 and 3 together, the memory array 100 can include a plurality of contact lines 102, a plurality of memory nodes 106 in direct contact with and stacked on the contact lines 102 via a plurality of conductive contacts 116, and a plurality of access lines 104 in direct contact with the memory nodes 106. The contact and access lines 102 and 104 can be at an angle α based on a first distance a between two adjacent contact lines 102 and a second distance b between two access lines 104. For example, the angle α may be determined according to the following formula:

$\alpha = {{arc}\; {\tan \left( \frac{b}{a} \right)}}$

In other embodiments, the value of α may be determined based on other suitable dimensions and/or conditions.

The individual contact and access lines 102 and 104 can include a trace, a channel, and/or other suitable structure constructed from doped polysilicon, a metal, a metal alloy, and/or other suitable materials. The conductive contacts 116 can include a volume of a metal (e.g., copper, aluminum, or gold), a metal alloy (e.g., solder), and/or other suitable conductive materials. The memory nodes 106 can include two memory cells 110 a and 110 b, as described in more detail below with reference to FIGS. 4A and 4B. Even though the contact and access lines 102 and 104 are shown as having generally rectangular shapes, in other embodiments the contact and access lines 102 and 104 may include curves, apertures, steps, and/or other structural features.

FIG. 4A is a perspective view of a two-cell memory node 106 useful for the non-orthogonal memory array 100 in FIG. 2 in accordance with embodiments of the technology. As shown in FIG. 4A, the memory node 106 includes a generally rectangular memory dielectric 130 having a first sidewall 132 a, a second sidewall 132 b, and a top wall 134 between the first and second sidewalls 132 a and 132 b. The memory dielectric 130 can include silicon dioxide, silicon nitride, and/or other suitable insulation materials.

The memory node 106 can also include a doped material 131 on the top wall 134 of the memory dielectric 130. In the illustrated embodiment, the doped material 131 includes a first N-type region 136 a, a second N-type region 136 b, and a P-type region 138 therebetween. The P-type region 138 is between the first and second N-type regions 136 a and 136 b to form two back-to-back P/N junctions as the first and second rectifiers 108 a and 108 b (FIG. 1). Even though two N-type regions are illustrated in FIG. 4A, in certain embodiments, the memory node 106 may include two P-type regions separated by one N-type region. In further embodiments, the memory node 106 may include other components and/or structures for forming a JFET, a MOSFET, and/or other suitable rectifiers.

The memory node 106 also includes a first memory structure 140 a in direct contact with the first sidewall 132 a, and a second memory structure 140 b in direct contact with the second sidewall 132 b. In one embodiment, the first and second memory structures 140 a and 140 b (collectively referred to as “memory structures 140”) can include a layer of chalcogenide glass. In other embodiments, the memory structures 140 may include a floating gate transistor and/or other suitable materials and/or structures.

Even though the memory structures 140 are shown as being generally rectangular, in other embodiments, the memory structures 140 may have other configurations. For example, as shown in FIG. 4B, the first and second memory structures 140 a and 140 b have an L shape and are in direct contact with an insulating material 142 (e.g., silicon oxide). In further embodiments, the memory structures 140 may have other suitable configurations.

FIGS. 5A-5K are top and cross-sectional views of a portion of a semiconductor substrate material 150 undergoing a process useful for forming several embodiments of the non-orthogonal memory array 100 of FIG. 2 in accordance with embodiments of the technology. In the illustrated embodiment, the substrate material 150 includes a P-type dopant for illustration purposes. One of ordinary skill in the art would understand that the substrate material 150 may also include an N-type dopant or that it may be intrinsic (i.e., not doped).

FIGS. 5A and 5B are top and cross-sectional views of the substrate material 150 during an initial stage of the process in which the contact lines 102 are formed. As shown in FIGS. 5A and 5B, an N-type silicon material 151 can be blanket-deposited onto the substrate material 150 using chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), and/or another suitable technique, or may be formed by counterdoping the P-type silicon substrate.

Subsequently, a photoresist (not shown) may be deposited on the N-type silicon material 151 via spin coating or another suitable deposition technique. The photoresist may then be patterned to form a plurality of trenches. The term “patterning” as used hereinafter generally refers to the process of printing a desired pattern on a photoresist and subsequently removing certain portions of the photoresist to form the desired pattern in the photoresist using photolithography and/or another suitable technique.

With the patterned photoresist, portions of the N-type silicon material 151 may be removed to form first trenches 153. Suitable removal techniques can include wet etching, dry etching, reactive ion etching, and/or other suitable techniques. In the illustrated embodiment, the first trenches 153 extend through the N-type silicon material 151 into the substrate material 150. In other embodiments, the first trenches 153 extend through the N-type silicon material 151 to interface with the substrate material 150. In further embodiments, the first trenches 153 extend partially through the N-type silicon material 151 without reaching the substrate material 150.

After partially removing the N-type silicon material 151, the first trenches 153 may be filled with an insulation material to isolate the contact lines 102. For example, in one embodiment, a blanket insulation material 152 (e.g., silicon oxide) may be deposited onto the substrate material 150 and then removed to expose the top surface 151 a of the N-type silicon material 151. Suitable removal techniques include chemical mechanical polishing, electro-chemical mechanical polishing, and/or other suitable techniques.

FIGS. 5C and 5D are top and cross-sectional views of the substrate material 150 during an optional stage of the process in which the optional third rectifiers 112 are formed. Referring to both FIGS. 5C and 5D, the third rectifiers 112 can be formed by first patterning the substrate material 150 with a photoresist (not shown) to identify the desired implantation areas. Then, a P-type dopant can be implanted using diffusion, ion implantation, and/or another suitable technique. In one embodiment, the P-type dopant can have a concentration higher than that of the substrate material 150. In other embodiments, the P-type dopant may have other desired concentrations.

FIGS. 5E and 5F are top and cross-sectional views of the substrate material 150 during another stage of the process in which the conductive contacts 116 are formed. Referring to both FIGS. 5E and 5F, a contact dielectric 156 can be deposited onto the substrate material 150. The contact dielectric 156 can then be patterned with a photoresist and partially removed to form a plurality of second trenches 157. In the illustrated embodiment, the second trenches 157 have a T shape with a first end 158 a in direct contact with the optional third rectifier 112 and a second end 158 b generally planar with the contact dielectric 156. In other embodiments, the second trenches 157 can have a rectangular, oval, partially spherical, and/or another suitable type of shape. After forming the second trenches 157, a conductive material 158 can be deposited onto the contact dielectric 156 and subsequently polished to fill the second trenches 157. The conductive material 158 can include tungsten, copper, aluminum, gold, and/or another suitable material.

FIGS. 5G and 5H are top and cross-sectional views of the substrate material 150 during another stage of the process in which a plurality of memory nodes 106 are formed. During this stage, the memory dielectric 130 and an N-type material 136 can be deposited in a series onto a top surface 156 a of the contact dielectric 156. Subsequently, the N-type material 136 may be patterned with a photoresist (not shown) and doped with a P-type dopant to form the P-type regions 138 between the first and second N-type regions 136 a and 136 b.

After forming the P-type regions 138, the process can then include patterning the N-type material 136 and removing portions of the N-type material 136 and the memory dielectric 130 to form columns 160 as shown in FIG. 5G. Each of the columns 160 can have a first sidewall 160 a, a second sidewall 160 b, and a top wall 160 c therebetween. The first and second sidewalls 160 a and 160 b individually correspond to a pair of adjacent conductive contacts 116.

Subsequently, a conformal memory structure 140 may be deposited on the columns 160 and the top surface 156 a of the contact dielectric 156. Then, the memory structure 140 may be spacer etched and/or otherwise selectively removed to form the first and second memory structures 140 a and 140 b on the first and second sidewalls 160 a and 160 b of the columns 160, respectively. Then, the columns 160 may be patterned and etched to form individual memory nodes 106, as shown in FIG. 5J.

Even though the foregoing description discusses forming the memory structures 140 as shown in FIG. 4A, in certain embodiments, the process can include stages for forming the memory structures 140 as shown in FIG. 4B. As shown in FIG. 5I, the process can include depositing a conformal layer of the memory structure 140 onto the columns 160 and the top surface 156 a of the contact dielectric 156. Then, the insulating material 142 may be deposited onto the memory structure 140 and polished to expose the columns 160. The insulating material 142 and the memory structure 140 can then be spacer-etched together to form L-shaped memory structures 140.

FIGS. 5J and 5K are top and cross-sectional views of the substrate material 150 during another stage of the process in which the access lines 104 are formed. As shown in FIG. 5K, an access dielectric 162 may be deposited onto the contact dielectric 156 and the memory nodes 106 and polished to form a generally flat surface 162 a. As shown in FIG. 5J, the access dielectric 162 may be patterned and etched to form third trenches 164 exposing the P-type regions 138 of the individual memory nodes 106. Subsequently, a conductive material 166 (e.g., copper) can be deposited in the third trenches 164 and on the top surface 162 a of the access dielectric 162. The deposited conductive material 166 can then be polished such that only those portions in the third trenches 164 remain, thus forming the access lines 104.

FIG. 6 is a schematic circuit diagram of a portion of an orthogonal memory array 200, and FIG. 7 is a top view of one implementation of the memory array 200 in FIG. 6 in accordance with embodiments of the technology. The memory array 200 can include components that are generally similar in structure and function to those of the memory array 100 in FIG. 1. As such, similar identification numbers generally refer to similar structure and/or components.

Referring to both FIGS. 6 and 7, the memory array 200 can include a grid 201 and a plurality of memory nodes 206 (identified individually as first to sixteenth memory nodes 206 a-206 p, respectively) carried by the grid 201. The grid 201 can include a plurality of first access lines 202 (identified individually as first to fourth contact lines 202 a-202 d, respectively) and a plurality of second access lines 204 (identified individually as first to eighth access lines 204 a-204 h, respectively). The first and second access lines 202 and 204 can be generally orthogonal relative to one another. The first and second access lines 202 and 204 can include a generally conductive trace constructed from a metal, a metal alloy, doped semiconductor material, and/or other suitable materials.

The memory nodes 206 are individually connected to the first and second access lines 202 and 204. As shown in FIG. 6, an individual memory node 106 can include a first memory cell 110 a, a first rectifier 108 a, a second rectifier 108 b, and a second memory cell 110 b connected to one another in a series. The input terminals of the first and second rectifiers 108 a and 108 b share an input point 114 that is electrically connected to corresponding first access lines 202. The output terminals of the first and second rectifiers 108 a and 108 b are electrically connected to the first and second memory cells 110 a and 110 b, which are in turn connected to corresponding second access lines 204, respectively.

Any of the memory nodes 206 that share a common first access line 202 do not share a common second access line 204. For example, the first memory node 206 a and the second memory node 206 b are both connected to the first access line 202 a. However, these two memory nodes 206 a and 206 b do not share a common second access line 204. Instead, the first memory node 206 a is connected to the first and second access lines 204 a and 204 b while the second memory node 206 b is connected to the third and fourth access lines 204 c and 204 d.

In operation, each of the memory cells 110 in the individual memory nodes 206 may be addressed or accessed by energizing a pair of corresponding first and second access lines 202 and 204. For example, the memory cells 110 of the tenth memory node 206 j may be accessed by energizing the first access line 202 c and one of the second access lines 204 c and 204 d. As shown in FIG. 6, the first access line 202 c and the second access line 204 c are energized (as indicated by the thickened lines) by having reversed polarity relative to other first and second access lines 202 and 204. As a result, electrical current flows from the first access line 202 c via the connection node 114, the first rectifier 108 a, and the first memory cell 110 a to the second access line 204 c. As a result, the state and/or other information stored in the first memory cell 110 a may be changed or read. While accessing the first memory cell 110 a, the second memory cell 110 b is not altered because the second access line 204 d connected to the second memory cell 110 b is biased with the same polarity as the first access line 202 c. After the first memory cell 110 a is accessed, the second memory cell 110 b may be accessed by energizing the first access line 202 c and the second access line 204 d. As a result, electrical current flows from the first access line 202 c via the connection node 114, the second rectifier 108 b, and the second memory cell 110 b to the second access line 204 d.

FIGS. 8A-8F are top and cross-sectional views of a portion of a semiconductor substrate material 250 undergoing a process useful for forming several embodiments of the orthogonal memory array 200 of FIG. 6 in accordance with embodiments of the technology. In the illustrated embodiment, the substrate material 250 includes a P-type dopant for illustration purposes. One of ordinary skill in the art would understand that the substrate material 250 may also include an N-type dopant or that the substrate material 250 may also be not doped.

FIGS. 8A and 8B are top and cross-sectional views of the substrate material 150 during an initial stage of the process in which the second access lines 204 are formed. As shown in FIGS. 8A and 8B, an N-type silicon material 251 can be blanket-deposited onto the substrate material 250 using chemical vapor deposition (CVD), plasma-enhanced vapor deposition (PEVD), and/or another suitable technique, or by counterdoping the P-type substrate with N-type dopants. Subsequently, the N-type silicon material 251 can be patterned using photolithography and partially removed to form a plurality of first trenches 253.

In the illustrated embodiment, the first trenches 253 extend through the N-type silicon material 251 into the substrate material 250. In other embodiments, the first trenches 253 extend through the N-type silicon material 251 to interface with the substrate material 250. In further embodiments, the first trenches 253 extend partially through the N-type silicon material 251 without reaching the substrate material 250. After partially removing the N-type silicon material 251, the first trenches 253 may be filled with an insulation material to isolate the contact lines 102 (not shown). For example, in one embodiment, a blanket insulation material 252 may be deposited onto the substrate material 250 and then removed to expose the top surface 251 a of the N-type material 251.

FIGS. 8C and 8D are top and cross-sectional views of the substrate material 150 during another stage of the process in which the conductive contacts 216 are formed following a process generally similar to that discussed above with reference to FIGS. 5E and 5F. FIGS. 8E and 8F are top and cross-sectional views of the substrate material 250 during another stage of the process in which the memory nodes 206 are formed following a process generally similar to that discussed above with reference to FIGS. 5G and 5H. However, unlike the embodiment illustrated in FIGS. 5G and 5H, the individual columns 160 do not share a common conductive contact 116. Instead, each conductive contact 116 is associated with only one column 160. Subsequently, the process may include forming individual memory nodes by patterning and etching the columns 160. The process may then include forming the first access lines 202 over the formed memory nodes 106 following a process generally similar to that discussed with reference to FIGS. 5J and 5K.

From the foregoing, it will be appreciated that specific embodiments of the technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the disclosure. Many of the elements of one embodiment may be combined with other embodiments in addition to or in lieu of the elements of the other embodiments. Accordingly, the disclosure is not limited except as by the appended claims. 

I/We claim:
 1. A memory structure, comprising: a dielectric having a first sidewall, a second sidewall, and a third wall between the first and second sidewalls; a first memory cell on the first sidewall; a second memory cell on the second sidewall; a doped material on the third wall of the dielectric, the doped material having a first portion, a second portion, and a third portion between the first and second portions, the first and second portions including a first dopant, the third portion including a second dopant different than the first dopant, a first rectifier coupled to the first memory cell, the first rectifier including the first and third portions of the doped material; and a second rectifier coupled to the second memory cell, the second rectifier including the second and third portions of the doped material, wherein the third portion of the doped material is configured to electrically isolate the first memory cell from the second memory cell.
 2. The memory structure of claim 1 wherein: the dielectric has a generally rectangular shape; the first and second memory cells include chalcogenide glass; the first and second portions of the doped material include an N-type material; and the third portion of the doped material includes a P-type material.
 3. The memory structure of claim 1 wherein the first and second memory cells include a layer of chalcogenide glass.
 4. The memory structure of claim 1 wherein: the dielectric is a first dielectric; the first and second memory cells have an L shape; and the memory structure further includes a second dielectric partially enclosed by the first and second memory cells.
 5. A method for manufacturing a memory structure, comprising: forming a first contact line and a second contact line in a substrate material, the first and second contact lines extending along a first direction; electrically connecting a memory node to the first and second contact lines, the memory node including a first memory cell electrically connected to the first contact line and a second memory cell electrically connected to a second contact line; forming an access line in and/or on the substrate material, the access line extending along a second direction different from the first direction; forming a rectifier device between the access line and the first and second memory cells; and electrically connecting the access line to the first and second memory cells, the access line, the first memory cell, and the first contact line forming a first circuit, the access line, the second cell, and the second contact line forming a second circuit electrically independent from the first circuit, wherein the first and second circuits include a common circuit path through at least a portion of the rectifier device.
 6. The method of claim 5 wherein: forming a first contact line and a second contact line includes: depositing a conductive material onto the substrate material; removing a portion of the deposited conductive material; forming the first and second contact lines with the remaining conductive material; and insulating the first and second contact lines with an insulation material; electrically connecting a memory node to the first and second contact lines includes: depositing a first dielectric onto the first and second contact lines; forming a plurality of openings in the first dielectric, the openings exposing the first and second contact lines; and depositing a first conductive material in the openings, and thereby forming a plurality of conductive contacts between the memory node and the first and second contact lines; and forming an access line in and/or on the substrate material includes: depositing a second dielectric onto the conductive contacts and the memory node; forming a trench in the second dielectric, the trench exposing at least a portion of the memory node and extending along a second direction that is at an oblique angle with the first direction; and depositing a second conductive material in the trench, and thereby forming the access line.
 7. The method of claim 5 wherein: forming a first contact line and a second contact line includes: depositing a conductive material onto the substrate material; removing a portion of the deposited conductive material; forming the first and second contact lines with the remaining conductive material; and insulating the first and second contact lines with an insulation material; and forming an access line in the substrate material includes: depositing a dielectric onto the memory node; forming a trench in the dielectric, the trench exposing at least a portion of the memory node and extending along a second direction that is at an angle of about 63° with the first direction; and depositing a conductive material in the trench, and thereby forming the access line.
 8. The method of claim 5 wherein: forming a first contact line and a second contact line includes: depositing a conductive material onto the substrate material; removing a portion of the deposited conductive material; forming the first and second contact lines with the remaining conductive material, the first and second contact lines having a first width a therebetween; and insulating the first and second contact lines with an insulation material; forming an access line in the substrate material includes: depositing a dielectric onto the memory node; forming a first trench and a second trench in the dielectric, the first and second trenches having a second width b therebetween and extending along a second direction forming an angle α according to the following formula: ${\alpha = {{arc}\; {\tan \left( \frac{b}{a} \right)}}};$ and depositing a conductive material in the first and second trenches, and thereby forming a first access line and a second access line.
 9. The method of claim 5 wherein: forming a first contact line and a second contact line includes: depositing a conductive material onto the substrate material; removing a portion of the deposited conductive material; forming the first and second contact lines with the remaining conductive material; and insulating the first and second contact lines with an insulation material; and forming an access line in the substrate material includes: depositing a dielectric onto the memory node; forming a trench in the dielectric, the trench exposing at least a portion of the memory node and extending along a second direction that is generally orthogonal to the first direction; and depositing a conductive material in the trench, and thereby forming the access line.
 10. A method for manufacturing a memory structure, comprising: forming a column on a substrate material, the column having a dielectric in direct contact with the substrate material and a doped material on the dielectric, the column having a first sidewall and a second sidewall, and the doped material including a first dopant; depositing a memory material on the column and the substrate material; selectively removing a portion of the memory material from the column and the substrate material such that a first portion of the memory material remains on the first sidewall and a second portion of the memory material remains on the second sidewall; and selectively introducing a second dopant into the doped material to form a common doping region in the doped material and two back-to-back junctions that share the common doping region.
 11. The method of claim 10 wherein forming a column on a substrate material includes: depositing the dielectric on the substrate; depositing the doped material on the dielectric; and selectively removing a portion of the dielectric and the doped material to form the column.
 12. The method of claim 10 wherein forming a column on a substrate material includes: depositing the dielectric on the substrate; depositing the doped material on the dielectric; and selectively removing a portion of the dielectric and the doped material to form the column.
 13. The method of claim 10 wherein: the first dopant includes an N-type dopant; and the second dopant includes a P-type dopant.
 14. The method of claim 10 wherein depositing a memory material includes depositing a memory material containing chalcogenide glass.
 15. The method of claim 10 wherein: the column includes a third wall between the first and second sidewalls; depositing a memory material includes depositing a memory material containing chalcogenide glass onto the first and second sidewalls and the third wall; and selectively removing a portion of the memory material includes selectively removing a portion of the memory material from the third wall of the column and the substrate material such that the first portion of the memory material remains on the first sidewall and the second portion of the memory material remains on the second sidewall.
 16. The method of claim 10 wherein: the column includes a third wall between the first and second sidewalls; depositing a memory material includes depositing a memory material containing chalcogenide glass onto the first and second sidewalls and the third wall; and selectively removing a portion of the memory material includes spacer etching the memory material such that the first portion of the memory material remains on the first sidewall and the second portion of the memory material remains on the second sidewall.
 17. The method of claim 10 wherein: the dielectric is a first dielectric; and the method further includes: depositing a second dielectric on the memory material; and selectively removing a portion of the memory material by spacer etching the memory material and the second dielectric such that a first portion of the memory material and the second dielectric remains on the first sidewall and a second portion of the memory material and the second dielectric remains on the second sidewall.
 18. The method of claim 10 wherein: the dielectric is a first dielectric; and the method further includes: depositing a second dielectric on the memory material; selectively removing a portion of the memory material by spacer etching the memory material and the second dielectric such that a first portion of the memory material and the second dielectric remains on the first sidewall and a second portion of the memory material and the second dielectric remains on the second sidewall; and removing a portion of the column after removing a portion of the memory material, and thereby forming a plurality of discrete nodes. 